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// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
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package org.apache.juneau.annotation;

import static java.lang.annotation.ElementType.*;
import static java.lang.annotation.RetentionPolicy.*;

import java.lang.annotation.*;

import org.apache.juneau.transform.*;

/**
 * Associates {@link PojoSwap} and {@link Surrogate} classes with POJOs and bean properties.
 * 
 * <p>
 * This annotation can be used in the following locations:
 * <ul>
 * 	<li>Classes.
 * 	<li>Bean getters/setters/fields.
 * 	<li>Inside the {@link Swaps @Swaps} annotation.
 * </ul>
 * 
 * <h5 class='section'>See Also:</h5>
 * <ul>
 * 	<li class='link'><a class="doclink" href="../../../../overview-summary.html#juneau-marshall.SwapAnnotation">Overview &gt; juneau-marshall &gt; @Swap Annotation</a>
 * </ul>
 */
@Documented
@Target({TYPE,ANNOTATION_TYPE,FIELD,METHOD})
@Retention(RUNTIME)
@Inherited
public @interface Swap {

	/**
	 * The {@link PojoSwap} and {@link Surrogate} class.
	 * 
	 * <p>
	 * A synonym for {@link #value()}.
	 */
	Class<?> impl() default Null.class;

	/**
	 * Identifies the media types that this swap is applicable for.
	 * 
	 * <p>
	 * In the following example, the swap is only invoked by the JSON serializer:
	 * 
	 * <p class='bcode'>
	 * 	<ja>@Swap</ja>(impl=ToStringSwap.<jk>class</jk>, mediaTypes=<js>"&#42;/json"</js>)
	 * 	<jk>public class</jk> MyBean { ... }
	 * 
	 * 	<jk>public class</jk> ToStringSwap <jk>extends</jk> PojoSwap&lt;Object,String&gt; {
	 * 			<jk>public</jk> String swap(BeanSession session, Object o) <jk>throws</jk> Exception {
	 * 				<jk>return</jk> o.toString();
	 * 			}
	 * 		}
	 * </p>
	 * 
	 * <h5 class='section'>See Also:</h5>
	 * <ul>
	 * 	<li class='link'><a class="doclink" href="../../../../overview-summary.html#juneau-marshall.PerMediaTypePojoSwaps">Overview &gt; juneau-marshall &gt; Per-media-type PojoSwaps</a>
	 * </ul>
	 */
	String[] mediaTypes() default {};

	/**
	 * Identifies a template string along with this swap.
	 * 
	 * <p>
	 * Template strings are arbitrary strings associated with swaps that help provide additional context information
	 * for the swap class.
	 * They're called 'templates' because their primary purpose is for providing template names, such as Apache FreeMarker
	 * template names.
	 * 
	 * <p>
	 * The following is an example of a templated swap class used to serialize POJOs to HTML using FreeMarker:
	 * 
	 * <p class='bcode'>
	 * 	<jc>// Our templated swap class.</jc>
	 * 	<jk>public class</jk> FreeMarkerSwap <jk>extends</jk> PojoSwap&lt;Object,Reader&gt; {
	 * 
	 * 		<jk>public</jk> MediaType[] forMediaTypes() {
	 * 			<jk>return</jk> MediaType.<jsm>forStrings</jsm>(<js>"&#42;/html"</js>);
	 * 		}
	 * 
	 * 		<jk>public</jk> Reader swap(BeanSession session, Object o, String template) <jk>throws</jk> Exception {
	 * 			<jk>return</jk> getFreeMarkerReader(template, o);  <jc>// Some method that creates raw HTML.</jc>
	 * 		}
	 * 	}
	 * </p>
	 * <p class='bcode'>
	 * 	<ja>@Swap</ja>(impl=FreeMarkerSwap.<jk>class</jk>, template=<js>"MyPojo.div.ftl"</js>)
	 * 	<jk>public class</jk> MyPojo {}
	 * </p>
	 * 
	 * <h5 class='section'>See Also:</h5>
	 * <ul>
	 * 	<li class='link'><a class="doclink" href="../../../../overview-summary.html#juneau-marshall.TemplatedSwaps">Overview &gt; juneau-marshall &gt; Templated Swaps</a>
	 * </ul>
	 */
	String template() default "";

	/**
	 * The {@link PojoSwap} and {@link Surrogate} class.
	 * 
	 * <p>
	 * A synonym for {@link #impl()}.
	 */
	Class<?> value() default Null.class;
}